Why summers at the north pole are cold

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A large proportion of the energy that does arrive impinges on white ice or snow surfaces and is mostly reflected away.

This means that more sea ice is formed in response to the increasing cold, which in turn increases the total albedo levels.

This then results in even more solar radiation being reflected. Climate researchers refer to such self-amplifying processes as positive feedback. Where the sea and air are warm, greater amounts of water evaporate, and clouds are formed. In colder areas, however, evaporation rates are low. Water is an extremely versatile element of our climate system.

This odourless and invisible gas is formed when liquid water evaporates. This amount represents about 0. If all of the water vapour in the atmosphere were to condense and fall to the surface as rain, it would cover the entire globe with a layer of water about 25 millimetres thick. Still, the proportion of water vapour in the air by mass is on average only 0. However, this average value is misleading because water vapour is distributed very unevenly throughout the atmosphere.

Its concentration decreases rapidly with increasing elevation, due in part to the fact that warm air can hold more water vapour than cold air. Accordingly, large amounts of water can be converted into water vapour in warm regions and less in colder regions. In the polar regions, because of the low temperatures, evaporation and water-vapour content in the atmosphere are very low in winter.

The water-vapour capacity of the atmosphere increases with every degree Celsius of air temperature. As an example, one cubic metre of air at a temperature of minus 20 degrees Celsius can hold at most 1.

However, if this volume is heated to plus 20 degrees Celsius, it can contain a maximum of The moisture does not remain in the atmosphere for long, however. Within ten days it falls to the Earth again as precipitation. When meteorologists report a condition of high humidity, this means that the air contains a large amount of water vapour. The most common measure used is relative humidity in per cent. Because a given volume of air at a given temperature and pressure can only hold a certain maximum amount of water vapour, we refer to a relative humidity of per cent when this maximum amount is reached.

As a general rule, when water evaporates over the sea or on land, no more than ten days will pass before the water vapour leaves the atmosphere again in the form of precipitation. In contrast to carbon dioxide, which may be retained for several centuries, water vapour leaves the atmosphere rather quickly and it is thus referred to as short-lived. Nevertheless, water vapour is regarded as the most important natural greenhouse gas.

Firstly, this is because it occurs in higher concentrations in the atmosphere than carbon dioxide, methane or nitrous oxide laughing gas. Secondly, it contributes two to three times more to the natural greenhouse effect than does carbon dioxide. The atmosphere has to contain water vapour before fog or clouds can form. However, the water vapour only condenses when the air is supersaturated with the gas, i. This supersaturation occurs when warm humid air masses rise and are cooled, and thus lose their capacity to absorb more water vapour.

The gas condenses into small droplets or, in certain circumstances, into small ice particles that waft freely in the air and commonly become visible from the ground as clouds or fog. There are two ways in which clouds are important for the global climate. Instead, they are deflected in many different directions. A certain portion even escapes back into space.

Ultimately, therefore, less solar radiation reaches the ground than it would if there were no cloud cover. As a consequence, the cloud cover effectively cools the Earth.

On the other hand, however, clouds also block the long-wave heat radiation rising from the Earth. In this way clouds can also contribute to warming in the atmosphere. Which of the two features is dominant depends upon the type of cloud. Clouds are most commonly differentiated based on their altitude and form. Visibly thick, low-hanging clouds primarily reflect the incoming sunlight and cool the Earth. High thin clouds, on the other hand, let the solar radiation through.

They subsequently block the outgoing heat radiation from the Earth and absorb a large portion of the thermal energy. The day-night effect also plays a role. Freeze-dried air The Arctic and Antarctic are fundamentally different with regard to the influence of clouds.

While dense fog and cloud cover are phenomena often observed during the summer in the Arctic — much to the dismay of polar explorers who usually plan their expeditions for the summer — in Antarctica they normally only form in coastal areas. The air above central Antarctica is simply too cold due to the limited amount of solar radiation, and therefore contains too little water vapour for condensation to form a thick cloud cover.

Instead, with increasing cold, all of the residual moisture condenses into ice crystals and falls to the ground as a form called diamond dust. For comparison: In Germany around litres of precipitation per square metre fall each year.

The same amount is also recorded at the weather station on the Antarctic Peninsula. In the coastal area of the Weddell Sea, i. In central Antarctica, on the other hand, annual precipitation rates are less than 50 litres per square metre over vast areas because of the extremely dry air. Only under exceptional conditions have meteorologists reported a thin veil of clouds over the Antarctic Ice Sheet.

However, these are not substantial enough to prevent the ice surface from radiating the small amount of incident heat back into space, which leads to further cooling of the air above Antarctica. In the Arctic, on the other hand, water vapour, clouds and fog can promote warming, especially in summer. One reason for this is the shrinking of the sea-ice cover in the Arctic Ocean during the summer.

Because this is accompanied by a corresponding warming of the air, the atmosphere can absorb more moisture. The humidity increases, so that only small soot, dust or salt particles in the air are required for the water vapour to condense and form clouds or fog.

In addition to the fact that clouds can be formed from it, water vapour possesses another property that is significant for the heat balance and weather patterns: It stores heat energy. This heat cannot be detected by a thermometer or felt by humans.

Meteorologists therefore refer to it as latent heat. It is sometimes referred to as evaporation heat because its value corresponds precisely to the energy originally required to evaporate the water.

What is special about the heat storage of water vapour, however, is that as soon as the vapour condenses into water droplets in the atmosphere, the stored heat from evaporation is released again as condensation energy and warms the surrounding air. In regions with high atmospheric water-vapour content, this effect causes additional warming. In areas with low humidity or little water vapour in the atmosphere, this effect is much less significant.

In some small depressions on the southern slope of the East Antarctic Ice Sheet, the paucity of water vapour is one of the reasons that it can get even colder than it does at the Vostok Research Station. In July and August, the air layer directly above the ice sheet becomes so cold that, according to scientific reckoning, it cannot become any colder. Minus 98 degrees Celsius seems to be the coldest temperature possible on the Earth under natural conditions.

For the air in the depressions to become this cold, a number of conditions must be met. Furthermore, the air above the snow-covered ice sheet may not contain any water vapour that could give off heat in the case of condensation, or could absorb radiation energy reflected from the snow and then be held in the atmosphere.

In any of these areas, you'll find an inhospitable, unpredictable but magnificent land of flat, treeless tundra with once-in-a-lifetime wildlife viewing. This can include polar bears, Arctic fox, musk ox and seals, among others. If you are determined to pass over the geographic North Pole, this is also possible but more expensive. You can book passage through several travel companies on the ice-breaker 50 Years of Victory.

All you may see in the spot is shifting sea ice, but some cruises combine this with hot-air balloon flights over the pole. Your best months in terms of daylight and weather are May through August. Northern lights are more prevalent in winter, however, and make their own magic. Obviously, whenever you visit the Arctic, let alone the North Pole, you'll need cold-weather clothes in your suitcase. Consider taking:. All rights reserved. By Teo Spengler ; Updated August 11, Heading into Arctic adventures It's one of the greatest remote travel adventures still available on the globe: a visit to the North Pole.

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